Acoustic tracking in shallow coastal areas on spawning migrations of pacific herring (Clupea pallasii) using ultrasonic telemetry

Abstract

The behavioral ecology of small pelagic fish has been studied by acoustic method for a long time. In particular, on pacific herring (Clupea pallasii), the behavioral ecology in shallow coastal areas which is observed spawning migration should be understood for the resource management and reproduction protection. In this study, supersonic telemetry was used for behavioral tracking of herring at shallow coastal areas. For the tracking, herring of regional group (n = 23) at Akkeshi bay (Depth ave. 5.78±2.15 m) in east Hokkaido were used. On the horizontal aspect, herring showed two migration patterns (pattern1: staying at the bay, pattern2: migration to Akkeshi lake (ave. 0.84±0.13 m) which is brackish water lake adjacent the bay). The lake is the main spawning grounds for herring, therefore the pattern 2 is indicated to be for spawning, and the pattern1 is before or after spawning. On the vertical aspect, diurnal distribution patterns were shown at the bay (day: ave. 5.41±3.78 m, night: ave. 3.83±2.60 m). Besides, the rapid horizontal migration was mainly observed at night. From these, the distribution patterns may influence on efficient migration at night without predation risk. Migration span at shallow coastal areas is estimated to be comparatively short, during 4-5 days.